1. Field of the Invention
The present invention relates to the field of wells. More specifically, the invention relates to a device and method for providing sand control within a well.
2. Description of Related Art
Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore has been drilled, the well must be completed before hydrocarbons can be produced from the well. A completion involves the design, selection, and installation of equipment and materials in or around the wellbore for conveying, pumping, or controlling the production or injection of fluids. After the well has been completed, production of oil and gas can begin.
Sand or silt flowing into the wellbore from unconsolidated formations can lead to an accumulation of fill within the wellbore, reduced production rates and damage to subsurface production equipment. Migrating sand has the possibility of packing off around the subsurface production equipment, or may enter the production tubing and become carried into the production equipment. Due to its highly abrasive nature, sand contained within production streams can result in the erosion of tubing, flowlines, valves and processing equipment. The loss of material from the reservoir matrix can also lead to the movement and possible collapse of the reservoir. The problems caused by sand production and the deterioration of the reservoir support matrix can significantly increase operational and maintenance expenses and can lead to a total loss of the well.
One means of controlling sand production is the placement of relatively large grain sand or resin beads, referred hereafter as xe2x80x9cgravelxe2x80x9d, within the perforation tunnels and/or the reservoir matrix. The gravel serves to consolidate and prevent the movement of failed sandstone and/or increase the compressive strength of the formation sand. It can also serve as a filter to help assure that formation fines and formation sand do not migrate with the produced fluids into the wellbore. In a typical gravel pack completion, gravel is mixed with a carrier fluid and is pumped in a slurry mixture through a conduit, often coiled tubing, into the wellbore. The carrier fluid in the slurry leaks off into the formation or is returned to the surface through a separate tubular or an annulus area, leaving the gravel deposited in the formation, perforation tunnels and wellbore where it forms a gravel pack. Gravel pack treatments typically include the running of a sand screen into the well prior to the gravel pack operation, but does not have to.
Other sand control methods include sand consolidation treatments that involve the use of a resin material. One method involves sand or gravel that is pre-coated with resin and is then pumped into the wellbore. The heat within the wellbore causes the resin to cure, thus joining the gravel together and forming a consolidated gravel plug. The consolidated gravel plug acts as a filter to restrict formation sand production and thereby stabilize the reservoir. An alternate method involves pumping sand and resin into the well where they mix and cure to form a consolidated sand plug. Yet another method involves pumping resin only into the formation, thereby forming an in-situ consolidation of the formation sand that stabilizes the reservoir. In methods that produce a consolidated sand plug within the wellbore, the sand plug can then be drilled out to open the wellbore for production and/or tubulars. The sand consolidation methods described above typically do not include a sand screen during the treatment. A sand screen can be is inserted within the wellbore after the consolidated sand plug is drilled out.
A problem that is frequently encountered in a sand control operation, especially in long or highly deviated sections or formations with high permeability, is the formation of gravel bridges within the wellbore. Non-uniform gravel distribution within the wellbore often occurs as a result of the premature loss of carrier fluid from the slurry. The fluid can be lost into high permeability zones within the formation, leading to the creation of gravel bridges in the wellbore, before all the gravel has been placed. These gravel bridges will restrict the flow of slurry in the wellbore and result in voids within the completion zone needing sand control. Effective control of formation sand during production requires complete coverage of the perforated interval. Voids within the sand control treatment allow formation sand and fines to be carried out of the reservoir matrix with the produced fluids and can lead to the problems mentioned above.
Once gravel bridging within the wellbore has occurred and the sand control operation is terminated, remedial treatments will need to be conducted for those sections that did not get an adequate gravel placement or consolidation treatment. This often includes multiple trips to drill out the gravel bridge so that subsequent sand control treatments can be performed, until a suitable treatment has been obtained through the entire zone of completion. This multiple trip approach increases the time and expense of completing the well, and also increases the risk of encountering wellbore problems, such as losing tools or becoming stuck.
Thus, despite the use of the prior art features, there remains a need for a sand control system and method that prevents or reduces the creation of gravel bridges and voids during a sand control completion of a wellbore.
To achieve such improvements, the present invention provides a system using a conduit run into a well on a service string. In one embodiment the conduit includes outlets along its length to permit the gravel slurry to exit the conduit along the length of the conduit and distribute the gravel slurry the full length of the conduit. The conduit can have a plurality of such outlets spaced to provide an even distribution of the sand control treatment and reduce the aforementioned problems. The conduit is attached to the delivery tubing (coiled tubing or service string tubing) via a releasable connector. The conduit is deployed on the delivery tubing and connector (and is in fluid communication therewith) in the well adjacent the area to be gravel packed. The gravel slurry is pumped into the well. Once the treatment is complete, the releasable connector is released to disconnect the conduit from the delivery tubing and the delivery tubing is removed from the well.
One embodiment of the present invention is a gravel pack system comprising a conduit having a plurality of outlets along its length, a delivery tubing extending to a well surface and a releasable connector releasably connecting the conduit to the delivery tubing. The conduit and the delivery tubing are in fluid communication. The conduit outlets can comprise perforations within the conduit, and can contain nozzles extending into the conduit. The conduit can also have baffle elements within its interior. The nozzles and baffle elements increase the pressure drop and turbulence that exists during a gravel pack operation and decrease the likelihood of gravel bridging within the conduit. To ease the drilling out of the conduit after the gravel pack operation is complete, the conduit can be made of an easily drillable material. It can also be made of a composite material.
Another embodiment is a sand control tool comprising a tubular conduit having a plurality of apertures along its length, the apertures capable of passing a gravel pack slurry, the tool being releasably connected to and in fluid communication with a work string. The apertures can contain nozzles having a known opening size. The tubular conduit can be made of an easily drillable material and can comprise baffle elements within its interior.
An alternate embodiment is a sand control system for completing a wellbore. The system includes a distribution tool comprising at least one conduit providing a plurality of outlets along the distribution tool length. A delivery tubing extends to a well surface and the distribution tool is in fluid communication with the delivery tubing. A releasable connector can be used to releasably connect the distribution tool to the delivery tubing. The distribution tool can be made of an easily drillable material. The distribution tool can comprise a plurality of flow paths through the distribution tool to differing depths within the wellbore. The distribution tool can comprise a plurality of concentric tubulars forming a plurality of flow paths to differing depths within the wellbore.
Yet another embodiment of the invention is a method for gravel packing a well. The method comprises extending a conduit having a plurality of outlets along its length in a well adjacent to a portion of the well to be gravel packed. The conduit is releasably attached to a delivery tubing. A gravel pack is pumped through the plurality of outlets into the well and the conduit is released from the delivery tubing. Excess gravel can be circulated out of the well through the delivery tubing after releasing the conduit from the delivery tubing. At least a portion of the conduit and gravel pack can be removed from the well by drilling or breaking the conduit into a plurality of sections. Some of the conduit outlets may contain nozzles that provide an increased pressure drop as the gravel pack is pumped through the conduit outlets. The conduit can be released from the delivery tubing by the rupture of a shear element, by actuating a mechanical J-slot tool or by a mechanical ball drop release mechanism.
Still another embodiment is a method of completing a well comprising pumping a gravel slurry through a perforated conduit. A perforated conduit can be placed at a predetermined location within the well the perforated conduit being attached to a work string with a releasable connector, the two being released from each other after pumping the gravel slurry. The perforated conduit can be drilled out after the release of the perforated conduit from the work string.
One particular embodiment is a method of inhibiting bridge formation during the completion of a well. The method comprises inducing an elevated pressure drop across a perforated conduit while pumping a sand control treatment. The perforated conduit can comprise nozzles located within the perforations and extending into the conduit and/or baffles within its interior to induce turbulence while pumping the gravel slurry. The perforations within the conduit are typically spaced along the conduit length for uniform distribution of the gravel slurry.
Another embodiment is a method for completing a wellbore comprising extending a distribution tool having a plurality of outlets along its length into the wellbore. A sand control treatment is pumped through the plurality of outlets into the wellbore. The distribution tool can be removed from the wellbore. The distribution tool can also be releasably attached to a delivery tubing, and can be disconnected from the delivery tubing after pumping the sand control treatment. The removal of the distribution tool can also be achieved by the drilled out of the distribution tool.